move a bunch of imports into TYPE_CHECKING blocks

These are only used for type checking, so don't bother importing them at
runtime.

Generally add future annotations at the same time, to make sure that
existing uses of these imports don't need to be quoted.

1 files changed, 10 insertions, 6 deletions

diff --git a/mesonbuild/scripts/depscan.py b/mesonbuild/scripts/depscan.py
index 3b26f92..6f92715 100644
--- a/mesonbuild/scripts/depscan.py
+++ b/mesonbuild/scripts/depscan.py
@@ -11,6 +11,7 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+from __future__ import annotations
 
 import json
 import os
@@ -20,9 +21,12 @@ import re
 import sys
 import typing as T
 
-from ..backend.ninjabackend import TargetDependencyScannerInfo, ninja_quote
+from ..backend.ninjabackend import ninja_quote
 from ..compilers.compilers import lang_suffixes
 
+if T.TYPE_CHECKING:
+    from ..backend.ninjabackend import TargetDependencyScannerInfo
+
 CPP_IMPORT_RE = re.compile(r'\w*import ([a-zA-Z0-9]+);')
 CPP_EXPORT_RE = re.compile(r'\w*export module ([a-zA-Z0-9]+);')
 
@@ -38,13 +42,13 @@ FORTRAN_USE_RE = re.compile(FORTRAN_USE_PAT, re.IGNORECASE)
 class DependencyScanner:
     def __init__(self, pickle_file: str, outfile: str, sources: T.List[str]):
         with open(pickle_file, 'rb') as pf:
-            self.target_data = pickle.load(pf) # type: TargetDependencyScannerInfo
+            self.target_data: TargetDependencyScannerInfo = pickle.load(pf)
         self.outfile = outfile
         self.sources = sources
-        self.provided_by = {} # type: T.Dict[str, str]
-        self.exports = {} # type: T.Dict[str, str]
-        self.needs = {} # type: T.Dict[str, T.List[str]]
-        self.sources_with_exports = [] # type: T.List[str]
+        self.provided_by: T.Dict[str, str] = {}
+        self.exports: T.Dict[str, str] = {}
+        self.needs: T.Dict[str, T.List[str]] = {}
+        self.sources_with_exports: T.List[str] = []
 
     def scan_file(self, fname: str) -> None:
         suffix = os.path.splitext(fname)[1][1:].lower()